added possibility for PlexConnect to start as linux daemon

normal usage:
 PlexConnect -logfile /var/PlexConnect.log

to stop it:
 type CTRL-C in console

daemon usage:
 PlexConnect_daemon.py -logfile /var/PlexConnect.log -pidfile /var/PlexConnect.pid

to stop it:
 kill `cat /var/PlexConnect.pid`